Method and means for cementing oil wells



May 13, 1930. F. w. HUBER METHOD AND MEANS FOR CEMENTING OIL WELLS Filed Dec. 27, 192,8

ATTORNEYS,

VPatented May 13, 1930 FREDERICK w. HUBER, or

RIVERSIDE, cALmoRNrA i vINIIEJJPIBIOID AND MEANS FOR CEMENTING OILVWELLS Application led December 27 1928., Serial lfm-328315.

This invention relates to improvements in methods for cementing oil wells, and the main object of the invention is to provide a simple, positive and effective method of ceinenting oil a well hole at a perforated por` tion of the casing for exclusion of intermediate and bottom waters.

Another object of my invention dis to provide an improved method for washing out or clearing the perforations, preparatory to cementing of. In makin an oil bore it is customary to carry the ore through the'V superficial formation to a point just above the lproductive horizon. Atthis point the socalled water string of casing 1s landed and cemented or otherwise sealed into place which excludes all of the water, penetrated, from the bore. The bore is then carried, at a smaller diameter, into the oil productive zone to the desired depth. Into this bore is inserted the oil string of casing which is perforated opposite the oil zone. In running inthe oil strin it is inevitable that some of the erforations become clogged with mud. his

factor causes a great deal of uncertainty in case it becomes necessary to make repairs for theexclusion of water.'

In the oil productive zones there are very often intermediate water sands or depleted 30 oil or gas sands which have become flooded vwith water; `or it not'infreq-uently happens `that the bore is carried beyond the oil zones into a lower zone which is water bearing and s o-called bottom water7 isencountered` The exclusion of these two types of water constitutes a most serious problem in oil production. 'In the art as heretofore practiced, it is custom aryto-v attempt to seal off intermediate water by the squeeze method? inV which thecement` grout isv pumped into the bore through tubing passing through a tight head at the top of the casing (at ground level) and suspendmgthis tubing well above theV -level at which the cementing operation is to be made. -The cement is pumped inand lls up the rforated casing for the desi-red distance.A he stem is' then sealed olf by means of the tig t head and a high pressure is applied by means of a pump to force the `-50 I cement through the perforations. there is no assurance that the erforations of the casino' are vall openthe cement will be forced out through those which happen to' be free, ,causing the cement grout to take a devious path and travelthrough and mix with the mud fluid. The applied pressure is not localized but is effective throughout the whole closed system and acts u on the exposed productive sands, forcing into them mud fluid which usually results in an impairment of their productivity.

My method, nowv to be described, I believe to be an improvement over any method hereltofore'in use for the exclusion of intermediate water after theoil String has been landed. I provide a positive means for opening and cleanino' the perforationsand washing the walls of the Ahole and so vintroducing the cement grout at the lowest level as to displace u ward the Huid in the hole without apprecia ly mixing the cement'grout with it andproducing atany desired level .and for any distance a substantial sleeve of cement on the outside of the perforated casing and bonded with it and the walls of the hole without subjecting the exposed oil sands to the pressure applied to the cement grout. 1 The accompanying drawings illustrateapparatus suitable for carrying out my invenso tion and referring thereto: Y

Fig. 1 is ayvertical section of the well hole, with the cleaning and cementing apparatus in place.

Fig. 2 is a vertical section of the piston or i swab.

' Fig. 3 lisa vertical section of the perforatedsection of a casing, showing'the beginning of the cement operation.

Fig. 4 is a view similar to Fig. 3 showing theend of the cementing'operatlon.

Fig. 5 is a vertical section of the cemented portion of the casing. afterthe cement in the casing has beenremoved by drilling.-

As shown in.Fig. 1, the apparatus used in l carrying out my invention comprises a tube o r 95 pipe 1, which is suspended vfreely inthe cas- 1ng 2,' andis connected by pipe 3 to'suitable .pumping means for'vsup'plymg liquid .for

cleaning the perforations or or supplying the cement, as hereinafter set forth,lsaid tubing 1 10 l being provided at its lower end with a piston, swab, or closure member 4, made of rubber or other suitable material which will make and maintain a snug fit with the interior of the as follows: It will be assumed that the holeperforated casing and be freely movable therein while maintaining a substantially watertight contact, The object of this piston or swab is to localize the applied pressure.

In Fig. 2 I show such a suitable piston or s wab fastened onto the end of the tubing, but

. I do not limit myself to this particular design of the piston as many other types of pistons will servetlie same purpose.

My improved'method may be carried out walls are covered more or less with a sheath of mud, which is usually the case -whe're the bore has been made with a rotarydrill. Below the vformation or strata to be sealed off a bridge, indicated at 5, is placed (as is usual in the art and well known) and the tubing, fitted within the piston or swab, is run-into `the casing and brought to rest just above the bridge. The upper end of the tubing (at ground surface) is connected through a pump to a supply of-water. AWater is pumped in. and the tubing is slowly raised at a volumetric rate lower than'the volumetric rate of tli'e pump: vThis maintains a localized pressure opposite -the lower end of the swab or piston and forcesopen the clogged perforations in the perforated section 2 of the casing, and

the velocity of the water impingin on the hole wall cuts away the adhering s eath of mud. This operation may be repeated in an upward andsdownward direction between the levels to be cemented, as many times as may be deemed necessary. The piston or swab has been found to be a most effective means of cleaning out the perforationsopposite the oil f sands.

-used as the washing fluid.

'at which the cement is being pumped in 'and an adequate localized pressure maintained in this manner. The cement passes through the cleared perforations and displaces the fiuid in the hole (mud and water) upwardly without appreciably 'mixing with it. The raising of.

the tubing is continued to the upper level of the zone to be cemented. yThe cement remaining in the tubing can then be washed out or displaced by a followingicolumn of water whilefthe tubing is raised above the upper level of` the cemented zone. The 'excess of cement can then be circulated out of the bore in the usualjmanner. The cement remaining on the inside of casing-is drilled out after it lias hardened.

Figs. 3 and 4 show the position of the piston 'or swab in the perforated casing at the beginning of the operation and at the end of the operation.- Fig. 5 shows the finished sleeve of cement, indicated at `6, after the cement in the perforated casing has been drilled out.

The above example illustrates average field practice and is typical of most of the operations which have to date been conducted by this method. Many modifications are possible, in all of which, however, the function of the piston is the same. `The essential feature of this invent-ion is the use of this piston or swab for cementing off intermediate and bottom waters through the perforated oil stringcasing substantially as described without imposing the applied pressure on the productive oil sands.

In the operation'described the tubing is not packed olf at ground surface by a ti ht head as is done in the oil art, but is suspeny ed freely inthe casing, everything but the tubing being at the prevailing atmospheric pressure.

The invention may also be carried out by closing thelcasing below the perforated section by bridge 4, and above suchsection by piston 3, uid cement being passed throug the tube by gravity until the space between such closures is filled with cement, and then the upper end of tube l may be closed by a plug or valve, and the tube and piston, together with the cement in the tube, may be orced down by the weight thereof, with the v addition of applied pressure, if necessa ,-so

as to force the cement through the ,per orations in the casing. i

I claim:

'1. The vmethod of cementing oil wells at y a perforated portion of a well casing which consists in bridging the well vhole below such perforated portion, fori'nin a closure for the well casing .adjacent and a ove the location of bridging, and progressively raising said closure while introducing cementing terial between the closure and the-bridging, under sufficient pressure to cause such material to be forced outA througli'the perfora- `tionsin the casing. f

2. The method which consists in forming a bridge below a perforated portion of awell casing, introducing into a well casin tubing open at the lower end and provided with a piston fitting in the perforated portion of the tubing into the space between the bridging and said piston and progressively raisin the tubingand piston at a volumetric rate w 'ch is lower than the volumetricfrate at which the cleaning fiuid is being supplied.

v3. The method which consists in forming a-bridge below a'perforated portion of a well casing, forcing cleaning fluid throu h the I scribed my name casing, introducing into a'wellbasin or tubing, open at its'- lower 'end and provi ed with l FREDERICK W. HUBER. 

